1. Field of the Invention
The present invention is directed generally to systems and methods for improving the picture quality of digital video.
2. Description of the Related Art
In the uncompressed domain, three picture quality parameters primarily determine the picture quality of digital video:                1. Frame size (which determines resolution or detail);        2. Frame rate (which determines fluidity of motion); and        3. Color depth (which determines quantization or the smoothness of shading).Color depth does not necessary refer to color (e.g., red, green, blue, and the like). Instead, color depth refers to a number of bits used to represent a portion (e.g., a pixel) of an image. For example, a grayscale image may have a color depth of 8 bits. This means each pixel has a color value between 0 (black) and 255 (white). Thus, color depth may also be referred to as a “pixel depth” or “bit depth” parameter.        
Increasing the value of each of the three picture quality parameters improves video quality under certain conditions. For example, by increasing the frame size, higher resolution digital video may be created. For example, 4K and 8K resolution video, which use large frame sizes (3840 pixels by 2160 pixels, and 7860 pixels by 4320 pixels, respectively), may be used to provide ultra-high resolution video.
By increasing frame rate, more realistic motion may be achieved. For example, movies are moving away from the historic frame rate of 24 frames per second (“fps”) to 48 fps. Further, even higher frame rates have been proposed (e.g., up to 120 fps for capture). Television sports programming has been forced to compromise and use smaller frame sizes (1280 pixels by 720 pixels) when offering higher frame rates (e.g., 60 fps) or use interlace scanning with larger frame sizes (e.g., 1920 pixels by 1080 pixels). Nevertheless, the trend is moving toward a frame size of 1920 pixels by 1080 pixels offered at a frame rate of 60 fps.
Further, the quality of digital video may be improved by increasing bit depth. For example, progress is being made to expand the bit depth in bits per pixel (“bpp”) beyond the traditional 8 bpp per color (i.e., a total of 24 bpp) to 10 bpp per color (i.e., a total of 30 bpp), or 12 bpp per color (i.e., a total of 36 bpp). Further, 16 bpp per color (i.e., a total of 48 bpp) have been proposed.
While increasing each of the three picture quality parameters may increase the picture quality of digital video, such increases also require more memory for image storage and higher bandwidth for transmission. FIGS. 1-3 illustrate such tradeoffs.
FIG. 1 is a graph in which the x-axis is bit depth measured in bpp and the y-axis is data (or bit) rate (uncompressed) measured in Gigabits per second (“Gbps”). Line 100 is plot of an uncompressed bitrate for digital video having the highest proposed (8K) frame size (or resolution) and the highest proposed frame rate (120 fps) as bit depth increases along the x-axis. The line 100 illustrates a large increase in uncompressed bitrate as the number of bpp (bit depth) increases. This means the interface bandwidth needed to send uncompressed 8K digital video ranges from about 48 Gbps to over 140 Gbps (if deep color at 12 bits per pixel, per color (i.e., a total of 36 bpp) is used).
FIG. 2 is a graph in which the x-axis is frame rate measured in fps and the y-axis is data (or bit) rate (uncompressed) measured in gigabits per second. Line 200 is plot of an uncompressed bitrate for digital video having the highest proposed (8K) frame size (or resolution) and a bit depth of 4:4:4 (i.e., a total of 24 bpp) as the frame rate increases along the x-axis. The line 200 illustrates an increase in uncompressed bitrate as the frame rate increases from 24 fps to 120 fps. In this example, the bandwidth requirements for 8K digital video increases from just under 20 Gbps to about 96 Gbps.
FIG. 3 is a graph in which the x-axis is frame size measured in pixels and the y-axis is data (or bit) rate (uncompressed) measured in gigabits per second. Line 300 is plot of an uncompressed bitrate for digital video having a frame rate of 120 fps and a bit depth of 4:4:4 (i.e., a total of 24 bpp) as the frame size increases along the x-axis. The line 300 illustrates the increase in uncompressed bitrate as the frame size (resolution) increases from 1280 pixels by 720 pixels to 8K pixels. In this example, the increase in bitrate appears to be somewhat modest until the frame size exceeds 4K at which point the bitrate increases dramatically to about 96 Gbps.
In currently available digital video systems, a single value for each of the three picture quality parameters is designated for video in both the compressed and uncompressed domains. Further, decoders are designed with those picture quality parameter values in mind and optimized to operate with just a few settings. While some minor changes to the values of picture quality parameters are possible (for example changes to the value of the frame size parameter), such changes are disruptive and cannot be performed dynamically.
Therefore, a need exists for methods and systems that adjust the values of the three picture quality parameters without undesirable disruptions in the picture quality and in the content delivery ecosystem. Systems and methods that make such adjustments dynamically based on the content of the digital video would be particularly desirable. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures.